179Epithelial–mesenchymal transition (EMT) is one of the bio-
logical processes involved in the genesis of CTC from primary
tumor sites [ 11 , 12 ]. EMT is a normal biological process, which is
critical during embryogenesis as development and growth of vari-
ous tissues are dependent on this process. This process changes the
primary cancer cell phenotype and leads to change in its cellular
polarity and loss of cell-cell adhesions, which further enhances the
motility and extravasation of CTCs into the bloodstream. The
reverse process of EMT, known as mesenchymal to epithelial tran-
sition (MET), allows CTCs to modify its phenotypes to get resis-
tant to physical stress in blood vessels and to chemoradiation
therapies [ 13 , 14 ].CTCs and its clinical and biological implications are often reported
in lung, breast, prostate, and colorectal carcinomas and much
less information are currently available for other carcinomas. In
esophageal cancers, CTC isolation is mostly reported in East Asian
populations with esophageal squamous cell carcinomas. Least
data is available from the Western population with esophageal
adenocarcinomas.
Adenocarcinoma of the esophagus is a histological subtype of
esophageal carcinoma where inflammation plays a key contribu-
tory role in tumor initiation and progression in the esophagus
(gastroesophageal reflux disease → Barret esophagus → esopha-
geal adenocarcinoma). In adults, chronic inflammatory responses
and its associated tissue damages are controlled by EMT process
[ 15 ]. There is substantial evidence that in carcinomas such as
esophageal adenocarcinomas, this control mechanism of EMT
steer the carcinogenesis process towards much aggressive and1.2 CTCs
in Esophageal
Adenocarcinomas
Fig. 1 CTC detection. Isolation of CTC and labeling of cytokeratin using immuno-
fluorescence. DAPI (4′,6-diamidino-2-phenylindole), the blue counterstain, was
used to stain the nucleus of the fixed CTC cellCirculating Tumour Cells